This invention relates to a process for producing ethylidenediacetate which comprises causing hydrocarbonylation reaction of methyl acetate or dimethyl ether with carbon monoxide and hydrogen.
In the prior art, ethylidenediacetate was synthesized from acetylene and acetic acid or by reacting acetaldehyde with acetic anhydride.
Recently, a process for producing ethylidenediacetate by reacting methyl acetate or dimethyl ether with carbon monoxide and hydrogen in the presence of a catalyst was proposed (refer to Japanese Patent Publication (laid open) No. 115409/1976). In the process disclosed in this Patent Publication, noble metals belonging to Group VIII of the Periodic Table and halides were essential components of the catalyst for hydrocarbonylation reaction. There is the passage "co-catalysts can be used together with the noble metal catalyst in order to enhance the reactivity" in the Patent Publication.
Furthermore, in Working Examples 1-29 of the Patent Publication, only rhodium or palladium was used as the main catalyst. However, in Working Examples 5 and 8, little ethylidenediacetate is formed in the absence of an organic or inorganic co-catalyst. In other words, the invention of Patent Publication No. 115409/1976 relates to a process for synthesizing ethylidenediacetate from methyl acetate or dimethyl ether carbon monoxide and hydrogen in the presence of a catalyst composed of a main component selected from rhodium, palladium, rhodium halides or palladium halides and a co-catalyst selected from organic compounds or inorganic compounds (Example 5 and 8). However, noble metals are expensive [refer to Hydrocarbon Process 54 June 83 (1975)] so if a noble metal is used as the catalyst for carrying out a reaction on an industrial scale, loss of the noble metal catalyst should be prevented. For example, KAKTAF 29 (5) page 376, 1975 discloses a process for preventing a rhodium complex from being reduced to metallic rhodium under a reducing atmosphere. Japanese Patent Publication (laid open) No. 90204/1978 discloses a process for preventing rhodium from evaporating from the reaction system during separation of the product, thereby leaking out of the reaction system. In a process for producing ethylidenediacetate, the equipment for preventing loss of the noble metal catalyst is complicated. This is one of the shortcomings in the synthesis of ethylidenediacetate.